About the Crown Molding Calculator
This crown molding calculator gives the miter and bevel settings for cutting crown molding flat on a compound miter saw, for any wall corner angle and any spring angle. It also shows the simpler miter setting for cutting the molding "nested" (upside down and leaning against the fence at its installed angle), and estimates the linear feet and number of pieces to buy for your room.
It is for DIYers and finish carpenters dealing with walls that are not exactly 90°, bay windows with 135° corners, or molding with an unusual spring angle. The spring angle is the angle the molding makes with the wall; most stock crown is 38° (sold as 52/38) or 45° (45/45), and some is 52°.
Measure the actual corner with an angle finder rather than assuming 90°. Outside corners use the same angles as the matching inside corner with the cut direction reversed; cut a test pair from scrap before cutting good stock.
With the default inputs, the miter angle (cutting flat) is 31.62 °. Change any value above to recalculate instantly.
How to use the crown molding calculator
- 1Find the spring angle of your crown (printed on the label or measured with a square).
- 2Measure the wall corner with an angle finder and enter it.
- 3Set the miter and bevel shown to cut the molding flat, or use the nested miter.
- 4Enter the room perimeter to see how many pieces to buy.
- 5Cut a test pair from scrap and check the fit before cutting good stock.
Formula and method
When crown molding is cut lying flat on the saw table, the cut is a compound angle that depends on both the wall corner angle W and the spring angle S (the angle between the back of the molding and the wall). The miter setting is arctan(sin S ÷ tan(W/2)) and the bevel setting is arcsin(cos S × cos(W/2)). For the common 38° crown in a 90° corner this gives 31.62° miter and 33.86° bevel; for 45° crown it gives 35.26° and 30°.
When the molding is cut nested — upside down, leaning against the fence exactly as it sits on the wall — the saw only needs a plain miter equal to half the angle that the corner turns, (180° − W)/2, which is 45° for a square corner. Material needed is the room perimeter plus a waste allowance for miters, copes and test cuts.
- S
- Spring angle of the molding (°)
- W
- Wall corner angle (°), e.g. 90 for square
Worked examples
52/38 crown in a square corner
With S = 38° and W = 90°, the miter is arctan(sin 38° ÷ tan 45°) = arctan(0.6157) = 31.62° and the bevel is arcsin(cos 38° × cos 45°) = 33.86°. A 52 ft room plus 15% waste needs 59.8 ft, or four 16 ft pieces.
45/45 crown in a square corner
For 45° crown, sin 45° ÷ tan 45° = 0.7071, so the miter is 35.26°, and the bevel is arcsin(0.7071 × 0.7071) = arcsin(0.5) = 30°.
52/38 crown around a 135° bay window corner
Half of 135° is 67.5°, whose tangent is 2.414. The miter is arctan(0.6157 ÷ 2.414) = 14.31° and the bevel is arcsin(0.788 × 0.3827) = 17.55°. Cut nested, the miter is simply (180 − 135) ÷ 2 = 22.5°.
Frequently asked questions
What are the miter and bevel angles for crown molding?+
For standard 52/38 crown in a 90° corner, cutting flat, set the miter to 31.62° and the bevel to 33.86°. For 45/45 crown use 35.26° miter and 30° bevel. Many compound miter saws have detents at these settings.
What is the spring angle of crown molding?+
It is the angle between the back of the molding and the wall when installed. Most stock crown has a 38° spring (called 52/38) and some has 45°. Hold the molding in a framing square to measure it.
Is it easier to cut crown molding upside down?+
Cutting nested — upside down and leaning against the fence at its spring angle — needs only a miter (45° for square corners) and no bevel. It is simpler but limited by the height of your saw fence.
How do I cut crown molding for corners that are not 90°?+
Measure the corner with an angle finder, then enter that angle here. The calculator splits the corner equally between the two pieces and gives the matching miter and bevel for each.
How much crown molding should I buy?+
Measure the room perimeter and add 10–15% for waste. Buy the longest pieces you can transport so long walls need no joints, and join shorter pieces with scarf cuts over a stud.